In recent years, the Internet is spreading rapidly, so as to advance increase in multiplicity and volume of information. In conjunction therewith, research and development activities are also active on next-generation radio access systems for implementing high-speed wireless communication in the field of mobile communication. One of such next-generation radio access systems is, for example, an HSDPA (High Speed Downlink Packet Access) system using adaptive modulation and error correction coding (AMC: Adaptive Modulation and channel Coding) to determine the throughput according to a reception environment of a mobile communication terminal (mobile equipment). The use of this HSDPA system enables a dramatic improvement in throughput. However, the dramatic improvement in throughput requires mobile communication terminals with better reception sensitivity when compared to the conventional W-CDMA technology.
One of techniques for improving the reception sensitivity of the mobile communication terminal is the receiver diversity technology of equipping the mobile communication terminal with a plurality of receivers and combining or selecting signals received through a plurality of antennas. Patent Document 1 below discloses the technology about diversity reception.
The flow of a signal processed in a conventional W-CDMA terminal will be described referring to a circuit configuration diagram of the W-CDMA terminal shown in FIG. 1 (which is a terminal without receiver diversity). First, a received signal received through antenna 81 is amplified still in the RF (Radio Frequency) band by LNA (Low Noise Amp; low noise amplifier) 82. Then the amplified signal is downconverted by Down converter (downconverter) 83, and this downconverted signal is linearly amplified by AGC (Automatic Gain Control; automatic gain control amplifier) 84. Next, the linearly amplified signal is subjected to quadrature detection by Quadrature detector (quadrature detection unit) 85, and this quadrature detected signal is converted into a digital signal by A/D converter 86. Thereafter, the converted digital signal is demodulated by Digital base band circuitry 90.    Patent Document 1: Japanese Patent Application Laid-open No. 8-79146